1. Field
The invention relates to an organic-light emitting display device.
2. Description of the Related Art
Organic light-emitting display devices, which are self-light-emitting display devices, have been in the spotlight as next-generation display devices because they provide high luminance, require low driving voltages, and can be made to be ultra-thin. In the meantime, in an analog driving method, which is generally applied to organic light-emitting display devices, a grayscale is represented by controlling the amount of current flown into each organic light-emitting element. The characteristics of a driving transistor for driving an organic light-emitting element in each pixel may vary due to process variations, and thus, the amount of light emitted by an organic light-emitting element may vary from one pixel to another pixel even in response to the same amount of current being flown into each pixel. To address this problem, attempts have been made to apply a digital driving method to organic light-emitting display devices. In the digital driving method, a single frame may be divided into a plurality of sub-frames having different lengths, which can each be represented as 2n, and a grayscale (e.g., gray levels) can be represented based on the sum of the lengths of one or more sub-frames during which light is emitted.
However, as the size, resolution, and display quality of organic light-emitting display devices increase, the number of sub-frames required may also increase considerably. However, as the number of sub-frames of each frame increases, the amount of time that it takes to scan for each sub-frame decreases. As a result, each pixel may not be able to be fully charged with a data voltage, thereby resulting in a deteriorated quality of display. To improve the efficiency of charging each pixel with a data voltage, a precharge driving method has been developed in which a precharge voltage is applied, ahead of a data voltage, to each pixel of an organic light-emitting display device.
However, the amount of improvement of the charging characteristics of pixels by the precharge driving method may vary considerably from one position to another position in an organic light-emitting display device. Also, the supply of the precharge voltage to all pixels may result in a considerable increase in the power consumption of an organic light-emitting display device.